Theodosius I (Latin: Flavius Theodosius Augustus;[1] 11 January 347 – 17 January 395), also known as Theodosius the Great, was Roman Emperor from 379 to 395. Theodosius was the last emperor to rule over both the eastern and the western halves of the Roman Empire. On accepting his elevation, he campaigned against Goths and other barbarians who had invaded the Empire; he failed to kill, expel, or entirely subjugate them, and after the Gothic War they established a homeland south of the Danube, in Illyricum, within the empire's borders. He fought two destructive civil wars, in which he defeated the usurpers Magnus Maximus and Eugenius at great cost to the power of the Empire.

In about 373 he became governor of Upper Moesia and oversaw hostilities against the Sarmatians and thereafter against the Alemanni.[6] He was military commander (dux) of Moesia, a Roman province on the lower Danube, in 374. However, shortly thereafter, and at about the same time as the sudden disgrace and execution of his father, Theodosius retired to Hispania. The reason for his retirement, and the relationship (if any) between it and his father's death is unclear. It is possible that he was dismissed from his command by the emperor Valentinian I after the loss of two of Theodosius' legions to the Sarmatians in late 374.

The death of Valentinian I in 375 created political pandemonium. Fearing further persecution on account of his family ties, Theodosius abruptly retired to his family estates in the province of Gallaecia (present day Galicia, Spain and northern Portugal) where he adapted to the life of a provincial aristocrat.

From 364 to 375, the Roman Empire was governed by two co-emperors, the brothers Valentinian I and Valens; when Valentinian died in 375, his sons, Valentinian II and Gratian, succeeded him as rulers of the Western Roman Empire. In 378, after the disastrous Battle of Adrianople where Valens was killed, Gratian invited Theodosius to take command of the Illyrian army. As Valens had no successor, Gratian's appointment of Theodosius amounted to a de facto invitation for Theodosius to become co-Augustus of the East Roman Empire. After Gratian was killed in a rebellion in 383, Theodosius appointed his own elder son, Arcadius, to be his co-ruler in the East. After the death in 392 of Valentinian II, whom Theodosius had supported against a variety of usurpations, Theodosius ruled as sole Emperor, appointing his younger son Honorius Augustus as his co-ruler of the West (Milan, on 23 January 393) and by defeating the usurper Eugenius on 6 September 394, at the Battle of the Frigidus (Vipava river, modern Slovenia) he restored peace.

By his first wife, the probably Spanish Aelia Flaccilla Augusta, he had two sons, Arcadius and Honorius and a daughter, Aelia Pulcheria; Arcadius was his heir in the East and Honorius in the West. Both Aelia Flaccilla and Pulcheria died in 385.

His second wife (but never declared Augusta) was Galla, daughter of the emperor Valentinian I and his second wife Justina. Theodosius and Galla had a son Gratian, born in 388 and who died young, and a daughter Aelia Galla Placidia (392–450). Placidia was the only child who survived to adulthood and later became an Empress.

The Goths and their allies (Vandali, Taifalae, Bastarnae and the native Carpi) entrenched in the provinces of Dacia and eastern Pannonia Inferior consumed Theodosius' attention. The Gothic crisis was so dire that his co-Emperor Gratian relinquished control of the Illyrian provinces and retired to Trier in Gaul to let Theodosius operate without hindrance. A major weakness in the Roman position after the defeat at Adrianople was the recruiting of barbarians to fight against other barbarians. In order to reconstruct the Roman Army of the West, Theodosius needed to find able bodied soldiers and so he turned to the most capable men readily at hand: the barbarians recently settled in the Empire. This caused many difficulties in the battle against barbarians since the newly recruited fighters had little or no loyalty to Theodosius.

Theodosius was reduced to the costly expedient of shipping his recruits to Egypt and replacing them with more seasoned Romans, but there were still switches of allegiance that resulted in military setbacks. Gratian sent generals to clear the dioceses of Illyria (Pannonia and Dalmatia) of Goths, and Theodosius was able finally to enter Constantinople on 24 November 380, after two seasons in the field. The final treaties with the remaining Gothic forces, signed 3 October 382, permitted large contingents of barbarians, primarily Thervingian Goths, to settle south of the Danube frontier and largely govern themselves.

The Goths now settled within the Empire had, as a result of the treaties, military obligations to fight for the Romans as a national contingent, as opposed to being fully integrated into the Roman forces.[7] However, many Goths would serve in Roman legions and others, as foederati, for a single campaign, while bands of Goths switching loyalties became a destabilizing factor in the internal struggles for control of the Empire.

"... the anger of the Emperor rose to the highest pitch, and he gratified his vindictive desire for vengeance by unsheathing the sword most unjustly and tyrannically against all, slaying the innocent and guilty alike. It is said seven thousand perished without any forms of law, and without even having judicial sentence passed upon them; but that, like ears of wheat in the time of harvest, they were alike cut down."[8]

Theodosius was excommunicated by the bishop of Milan, Saint Ambrose for the massacre.[9] Ambrose told Theodosius to imitate David in his repentance as he had imitated him in guilt — Ambrose readmitted the emperor to the Eucharist only after several months of penance.

In the last years of Theodosius' reign, one of the emerging leaders of the Goths, named Alaric, participated in Theodosius' campaign against Eugenius in 394, only to resume his rebellious behavior against Theodosius' son and eastern successor, Arcadius, shortly after Theodosius' death.

The administrative divisions of the Roman Empire in 395, under Theodosius I.

After the death of Gratian in 383, Theodosius' interests turned to the Western Roman Empire, where the usurper Magnus Maximus had taken all the provinces of the West except for Italy. This self-proclaimed threat was hostile to Theodosius' interests, since the reigning emperor Valentinian II, Maximus' enemy, was Theodosius' ally. Theodosius, however, was unable to do much about Maximus due to his still inadequate military capability and he was forced to keep his attention on local matters. Maximus hoped to share the Empire with Theodosius, but when Maximus began an invasion of Italy in 387, Theodosius felt compelled to take action. Both sides raised large armies which included many barbarians.

The armies of Theodosius and Maximus fought at the Battle of the Save in 388, which saw Maximus defeated. On 28 August 388 Maximus was executed.[10] Now the de facto ruler of the Western empire as well, Theodosius stayed in Milan until 391 installing his own loyalists in senior positions including the new magister militum of the West, the Frankish general Arbogast. Valentinian II was a very young man, little more than a figurehead, with Arbogast as the true power behind the throne.

Trouble arose again, after Valentinian quarreled publicly with Arbogast, and was found hanging in his room. Arbogast announced that this had been a suicide. Arbogast, unable to assume the role of Emperor because of his non-Roman background, elected Eugenius, a former teacher of rhetoric. Eugenius made some limited concessions to the Roman religion; like Maximus he sought Theodosius' recognition in vain. In January 393, Theodosius gave his son Honorius the full rank of "Augustus" in the West, citing Eugenius' illegitimacy.[11]

Theodosius gathered a large army, including Goths and other barbarians, and marched against Eugenius. The two armies faced at the Battle of Frigidus in September 394.[12] The battle began on 5 September 394, with Theodosius' full frontal assault on Eugenius' forces. Theodosius was repulsed on the first day, and Eugenius thought the battle to be all but over. However, in Theodosius' camp, the loss of the day decreased morale. It is said that Theodosius was visited by two "heavenly riders all in white" who gave him courage. The next day, the battle began again and Theodosius' forces were aided by a natural phenomenon known as the Bora, which produces cyclonic winds. The Bora blew directly against the forces of Eugenius and disrupted the line.

Eugenius' camp was stormed; Arbogast committed suicide and Eugenius was captured and soon after executed. Thus Theodosius became sole Emperor.

The Lateran obelisk was shipped to Rome soon afterwards, but the other one then spent a generation lying at the docks due to the difficulty involved in attempting to ship it to Constantinople. Eventually, the obelisk was cracked in transit. The white marble base is entirely covered with bas-reliefs documenting the Imperial household and the engineering feat of removing it to Constantinople. Theodosius and the Imperial family are separated from the nobles among the spectators in the Imperial box, with a cover over them as a mark of their status. The naturalism of traditional Roman art in such scenes gave way in these reliefs to conceptual art: the idea of order, decorum and respective ranking, expressed in serried ranks of faces. This is seen as evidence of formal themes beginning to oust the transitory details of mundane life, celebrated in Romanportraiture.

In 325, Constantine I had facilitated the Church's bishops to convene the Council of Nicea, which affirmed the prevailing view that Jesus, the Son, was equal to the Father, one with the Father, and of the same substance (homoousios in Greek). The council condemned the teachings of the heterodox theologian Arius: that the Son was a created being and inferior to God the Father. Despite the council's ruling, controversy continued. By the time of Theodosius' accession, there were still several different Church factions that promoted alternative Christology.

While the Nicene council paved the way for the homoousian view, there remained many closer to the Arian school who attempted to bypass the Christological debate by saying that Jesus was merely like (homoios in Greek) God the Father, without speaking of substance (ousia). These non-Nicenes were frequently labeled as Arians (i.e., followers of Arius) by their opponents, though not all would necessarily have identified themselves as such.[13]

The Emperor Valens had favored the group who used the homoios formula; this theology was prominent in much of the East and had under Constantius II gained a foothold in the West. Theodosius, on the other hand, steadfastly held to the Nicene Creed which was the interpretation that predominated in the West and was held by the important Alexandrian church.

Definition of orthodoxy and de-legitimation of non-orthodox Christian creeds[edit]

In May 381, Theodosius summoned a new ecumenical council at Constantinople (see First Council of Constantinople) to repair the schism between East and West on the basis of Nicean orthodoxy.[16] "The council went on to define orthodoxy, including the mysterious Third Person of the Trinity, the Holy Spirit, who, though equal to the Father, 'proceeded' from Him, whereas the Son was 'begotten' of Him."[17] The council also "condemned the Apollonarian and Macedonian heresies, clarified jurisdictions of the state church of the Roman Empire according to the civil boundaries of dioceses and ruled that Constantinople was second in precedence to Rome."[17] The death of Valens, the Arians' protector, probably damaged the standing of the Homoian faction.

The Christian persecution of Roman religion under Theodosius I began in 381, after the first couple of years of his reign in the Eastern Empire. In the 380s, Theodosius I reiterated Constantine's ban on former customs of Roman religion, prohibited haruspicyon pain of death, pioneered the criminalization of Magistrates who did not enforce laws against polytheism, broke up some pagan associations and tolerated attacks on Roman temples.

Between 389–392 he promulgated the "Theodosian decrees"[18] (instituting a major change in his religious policies),[19] which removed non-Nicene Christians from church office and abolished the last remaining expressions of Roman religion by making its holidays into workdays, banned blood sacrifices, closed Roman temples, and disbanded the Vestal Virgins.[20] The practices of taking auspices and witchcraft were punished. Theodosius refused to restore the Altar of Victory in the Senate House, as asked by non-Christian senators.[19]

In 392 he became sole Emperor (the last one to claim sole and effective rule over an Empire including the Western provinces). From this moment till the end of his reign in 395, while non-Christians continued to request toleration,[21][22] he ordered, authorized, or at least failed to punish, the closure or destruction of many temples, holy sites, images and objects of piety throughout the Empire.[23][24][25][26][27][28]

In 393 he issued a comprehensive law that prohibited any public non-Christian religious customs,[29] and was particularly oppressive to Manicheans.[30] He is likely to have disbanded the ancient Olympic Games, whose last record of celebration was in 393, though archeological evidence indicates that some games were still held after this date.[31]

Death of Western Roman Emperor Valentinian II, usurpation, and another civil war[edit]

On 16 May 392, Valentinian II was found hanged in his residence in the town of Vienne in Gaul. The Frankish general Arbogast, Valentinian's protector and magister militum, maintained that it was suicide. Arbogast and Valentinian had frequently disputed rulership over the Western Roman Empire, and Valentinian was also noted to have complained of Arbogast's control over him to Theodosius. Thus when word of his death reached Constantinople, Theodosius believed, or at least suspected, that Arbogast was lying and had engineered Valentinian's demise. These suspicions were further fueled by Arbogast's elevation of Eugenius, from Roman commander and official, to the position of Western Emperor. Ambrose, the Bishop of Milan, spoke some veiled accusations against Arbogast, in his funeral oration for Valentinian II.

Valentinian II's death sparked a civil war between Eugenius and Theodosius over the rulership of the west, resulting in the Battle of the Frigidus. The eastern victory there led to the final brief unification of the Roman Empire under Theodosius, and the ultimate irreparable division of the empire after his death.

Theodosius died, after suffering from a disease involving severe edema, in Milan on 17 January 395. Ambrose organized and managed Theodosius' lying in state in Milan. Ambrose delivered a panegyric titled De Obitu Theodosii[32] before Stilicho and Honorius in which Ambrose praised the suppression of paganism by Theodosius. Theodosius was finally buried in Constantinople on 8 November 395.[33]

Theodosius's army rapidly dissolved after his death, with Gothic contingents raiding as far as Constantinople. As his heir in the East he left Arcadius, who was about twelve years old, and in the West Honorius, who was eight. Neither ever showed any sign of fitness to rule, and their reigns were marked by a series of disasters. As their guardians Theodosius left Stilicho, who ruled in the name of Honorius in the Western Empire, and Flavius Rufinus who was the actual power behind the throne in the East.

^Grindle, Gilbert (1892) The Destruction of Paganism in the Roman Empire, pp.29–30. Quote summary: For example, Theodosius ordered Cynegius (Zosimus 4.37), the praetorian prefect of the East, to permanently close down the temples and forbade the worship of the deities throughout Egypt and the East. Most of the destruction in the East was perpetrated by Christian monks and bishops.